This invention relates generally to the formation of a hologram on a document or other article as part of a printing process.
Holograms and other types of diffraction gratings are commonly attached to a document or other article containing printing. An example is the attachment of holograms to credit cards in order to authenticate their genuineness and increase the difficulty of conterfeit credit cards being used. Holograms are used, or proposed to be used, as anti-counterfeiting devices on a number of other types of documents, such as stock certificates, identification badges, passports, and even currency. Holograms are also attached to printed documents and articles for other reasons, such as their decorative effect.
The predominant method of manufacturing such documents and articles currently being practiced involves separately manufacturing the printed document and the hologram, and then, as a last step, attaching the hologram to the printed document or article. The holograms are generally manufactured in the form of a roll of material, either having a simple pressure-sensitive adhesive on one side for attachment to such a document or article, or in the form of hot-stamped foil wherein the hologram is released from a carrier and attached to a document or article by application of heat and pressure. In either case, the hologram usually carries the holographic information in a surface relief pattern that is formed either by embossing into a film or by casting a liquid resin. The resulting surface relief pattern is metallized in order to form a reflective surface which diffracts incident viewing light into formation of a reconstructed image.
It is a primary object of the present invention to improve the efficiency, and thus reduce the cost, of the process for manufacturing documents or other articles that contain both printing and a hologram or other type of diffraction grating attached thereto.